| China is poor in oil but rich in coal. A great quantity of crude benzol would beobtained during the process of coking coal. Toluene as one of the most importantindustrial raw material can be obtained from crude benzol. But the coking tolueneobtained from the extraction distillation process contains many purities such aspyridines and thiophenes, which would affect the quality and application of toluene.This article summarized several methods of denitrogenation and desulfurization.Among these, adsorption has great application prospect, because of its simpleoperation, low cost, few pollution and good perfomances.Fix-bed vapor-phase adsorption and on-line stream regeneration were applied toinvestigate the adsorption and regeneration properties of NC zeolites. Results showthat the content of pyridines can be reduced to below500μg/g, when the adsorptiontemperature is115℃. Denitrogenation ability can be recovered after regenerationsalthough the treatment capacity decreases. The results of TGA and13C-NMR indicatethat the main reason of deactivation is coke formation.Ce4+, Ni2+and Cu+exchanged NC zeolites were prepared by liquid-phase ionexchange method and characterized by XRD, BET and ICP-OES techniques. Resultsof adsorbent screen experiment indicate that Ce4+exchanged zeolites have the bestperformances in model toluene. Results of batch and fix-bed experiments showed thatselectivities of thiophenes decrease as follows:2-methylthiophene>3-methylthiophene> thiophene. Higher adsorption temperature and vapor-phaseadsorption are beneficial to desulfurization.The adsorption desulfurization data of CeNC were fitted by adsorption isothermsand kinetic models. Chemisorption resistance is likely the rate controlling stage atlower adsorption temperature, while intraparticle diffusion resistance becomes moreimportant at higher temperature. The results of TGA analysis showed that thiophenesare mainly adsorbed by S-Ce bond but toluene forms π-electron interaction andπ-complexation with Ce3+and Ce4+. |
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